draw: rewrite primitive assembler

draw: rewrite primitive assembler

We can't be injecting the primitive id's in the pipeline because
by that time the primitives have already been decomposed. To
properly number the primitives we need to handle the adjacency
primitives by hand. This patch moves the prim id injection into
the original primitive assembler and completely removes the
useless pipeline stage.

Signed-off-by: Zack Rusin <zackr@vmware.com>
Reviewed-by: Roland Scheidegger <sroland@vmware.com>